Trimethylbenzoyl diphenylphosphine oxide (TPO), also known as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, is a Type I photoinitiator widely used in UV- and LED-curable cosmetic products such as gel nail polishes. It enables rapid polymerization, low yellowing, and durable film formation.
However, TPO has come under regulatory scrutiny. The European Commission classified it as a Category 1B reproductive toxicant under the 7ᵗʰ CMR Omnibus Regulation, triggering its ban in all EU cosmetics from September 1, 2025
The SCCS previously considered it safe in nail applications up to 5%, but no exemption dossier under Article 15 of the Cosmetics Regulation was submitted, making the ban absolute.
Consumer concern around reproductive toxicity and sensitization potential is accelerating industry movement toward alternative photoinitiators.
Why Replace TPO
Health & Regulatory Concerns
– Classified as a reproductive toxicant (CMR 1B).
– Moderate sensitizer, raising occupational safety issues for nail technicians.
Fully prohibited in EU cosmetics from September 2025.
Market Trends
– Rising consumer demand for “TPO-free” nail systems.
– Increased preference for LED-curable systems with safer photoinitiators.
Functional Rationale
– Alternatives must deliver fast curing under LED/UV, minimal yellowing, and good pigment penetration.
– Stability under cosmetic formulation conditions (pH ~6–7, exposure to light, solvents) is critical.
Regulatory Landscape for TPO
| Region / Authority | Current Status | Key Restrictions | Implication for R&D |
| European Union (EC) | Banned | Prohibited in cosmetics from Sept 1, 2025 (CMR 1B, Reg. 1223/2009, no exemption) | All EU-market nail products must reformulate without TPO |
| United States (FDA) | Permitted (no specific cosmetic restriction) | Governed under general cosmetic safety; no FDA positive list | Still usable, but EU bans may drive global reformulation |
| China (NMPA) | Case-by-case | Requires safety assessment; high likelihood of EU alignment | Safer path is TPO-free nail products |
| Japan (MHLW) | Permitted | Must be declared on label above thresholds | May remain allowed, but consumer pushback expected |
| Brazil (ANVISA) | Restricted | Aligns with EU precautionary measures | Reformulation expected in LATAM |
| Other LATAM (Mexico, Argentina, etc.) | Mixed | Varying rules, generally converging toward EU bans | TPO-free strategies preferred |
Manufacturers/Supplier of Alternatives
1. Wego Chemical Group (Global)
Wego supplies Photoinitiator TPO-L (ethyl trimethylbenzoyl phenylphosphinate), a liquid photoinitiator offering strong absorption at 350–400 nm, making it suitable for LED curing.
It provides fast curing with low yellowing, and is widely adopted as a safer TPO replacement. Wego supports global sourcing and provides technical datasheets.
2. Ningbo Inno Pharmchem (China)
Ningbo Inno manufactures high-purity TPO-L (>95%). It is offered in liquid form, optimized for LED-curable coatings and cosmetics.
The company provides bulk supply, sample support, and documentation for formulation R&D, though cosmetic-specific regulatory approval must be confirmed regionally.
3. Sigma-Aldrich / Merck (Global)
Sigma offers BAPO (Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, Irgacure 819), a Type I photoinitiator with strong radical generation efficiency.
Available at 97% purity, it is effective for pigmented and thick formulations due to its deeper curing profile. Widely used in industrial UV curing, but requires regulatory review for cosmetic-grade use.
4. Parchem (USA)
Parchem distributes BAPO (CAS 162881-26-7) at ≥97% purity, designed for UV-curable formulations.
The company offers regulatory support and custom sourcing for cosmetic and industrial R&D teams. Supply is available at both lab and bulk scales.
5. IGM Resins (Belgium)
IGM Resins produces Omnirad 819 (BAPO), optimized for curing pigmented and thick-section systems
It has high absorption up to ~410 nm, making it compatible with modern LED lamps. IGM offers strong technical service and global supply capability.
Formulation Considerations
- pH Compatibility: TPO alternatives (TPO-L, BAPO) are stable in typical nail gel systems (pH 6–7).
- Curing Efficiency: TPO-L cures efficiently at 365–400 nm (LED/UV), while BAPO extends to 410 nm, enabling curing of pigmented systems.
- Dosage: TPO was typically used at ≤5%. Alternatives may be effective at lower concentrations (e.g., 1–3%), but empirical PET (polymerization efficiency testing) is required.
- Stability: Both TPO-L and BAPO demonstrate low yellowing; antioxidants may still be added to enhance stability.
- Packaging: TPO-L (liquid) requires airtight containers to avoid light degradation, while BAPO (solid) is more stable in controlled storage.
Conclusion
The EU ban on TPO in cosmetics (September 2025) requires urgent reformulation of gel nail products. TPO-L and BAPO (Irgacure 819) are the most validated replacements, balancing curing efficiency, low yellowing, and broad supplier availability.
R&D teams should anticipate dosage optimization, solvent compatibility, and regulatory documentation needs.
Stay ahead of regulatory changes and consumer demand for safer cosmetics products. Submit your request through the form, and our team will guide you with proven TPO-free solutions tailored to your R&D needs.
